getDonations method
Will get a collection of PcoGivingDonation objects (expecting many)
using a path like this: https://api.planningcenteronline.com/giving/v2/batches/1/donations
Implementation
Future<PcoCollection<PcoGivingDonation>> getDonations(
{PcoGivingDonationQuery? query}) async {
query ??= PcoGivingDonationQuery();
var url = '$apiEndpoint/donations';
return PcoCollection.fromApiCall<PcoGivingDonation>(url,
query: query, apiVersion: apiVersion);
}